ASV RT-30 Timing issue?

Hi everyone, I bought a used ASV rt-30 which has had a new engine fitted after an insurance claim. It was bought as a non-runner, so I knew it was going to have some issues. I've only managed to get it started a few times, and when it ran it was running terribly, lots of black smoke and sounded very rough. now it just cranks and cranks and won't run. As I bought it so cheap I was happy to throw some money at it to get it going but nothing seems to be working. So far, I have replaced: lift pump, injectors rebuilt, injector pump rebuilt, glow plugs, glow plug relay, fuel shut solenoid, head gasket, head has been skimmed and tested. the compression also tests perfectly. To rule out the fuel feed system I hooked up a completely separate fuel tank before the lift pump and also rigged it up so the tank was on the roof of the machine gravity feeding directly into the injector pump inlet with no luck. Fuel is returning through the return lines as it started to overflow the main tank when I was testing with my separate tank. This has led me down a rabbit hole of checking the timing. I've pulled the timing case off to check for sheared pins but all seems well under there. The only thing I can't figure out is when the timing marks align on all three gears number one cylinder seems to be in the wrong spot, I was under the assumption it should be at 22deg BTDC, at the moment it seems to be about halfway down the bore after hitting TDC? Engine Perkins 403D-15 2800rpm, non turbo diesel. Any help would be greatly appreciated!